Nanoptronics Research Center- News
Ph.D. Thesis Defense

Restore images and colors  | Post date: 2021/10/25 | 
On 19 October 2021, Mr. Hossein Arab defended his Ph.D. thesis under the supervision of Prof. Shahram Mohammadnejad with the title of "Design, Simulation and Fabrication of Quantum Dot Single Photon Emitter for Quantum Information Processing".

Ph.D. Thesis Abstract:
One of the fascinating and challenging research fields is to pay attention to technology development of quantum photonic. In this regard, fabrication and development of single photon emitters is of the most important proceedings, which are required to reach telecommunications, calculations, and quantum information processing. One of the most principle challenges is attributable to design, simulation, and implementation of one ideal certain single-photon source, which enables to produce quantum distribution single-photons proportional to free-space communication windows (800 nm) and/or transmission ones in optical fiber (1330-1550 nm). Hence, different methods for producing single-photon sources have been introduced in recent years among which using graphene quantum dots is one of the newest ones. The aforementioned method will overcome both challenges of low-temperature performance and need to modern and expensive facilities in order to reach combined semiconductor quantum dots-based devices. Since graphene quantum dots are not capable of emitting light in near infrared ranges and so they cannot be used in free-space quantum communication applications, it was endeavored to investigate the simultaneous effect of doping of graphene quantum dots through selenium atoms and functionalizing the structure with nitrogenous functional groups for scrutinizing variations in the structure's emission spectrum. In this regard, according to the results obtained from atomic analysis, three structures based on pure graphene quantum dots, selenium-doped graphene quantum dots, and selenium-doped graphene quantum dots functionalized by amide groups were synthesized using chemical methods, and the effect of change of input parameters on the results of emission spectrum belonging to the structure arrayed was also investigated. The synthesis of all three structures was validated; their emission spectrum results showed emissions with the wavelength of 496 nm, 515-547 nm, and 761-787 nm, respectively. There is a good accordance between the results obtained in this research and the results of simulation and synthesis reported by other researchers. Moreover, single-photon experiments indicated very high single-photon purity having a value of second order correlation function lower than 0.5 for quantum dots synthesized; they also showed a 42% single-photon efficiency for the doped and functionalized structure, which is a very suitable platform for quantum communication and quantum information processing applications.

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